Problem: $ { \left[\begin{array}{rr}{-1} & {0} \\ {-1} & {3}\end{array}\right]+\left[\begin{array}{rr}{-2} & {0} \\ {0} & {2}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{-1}+{-2} & {0}+{0} \\ {-1}+{0} & {3}+{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-3} & {0} \\ {-1} & {5}\end{array}\right]}$